1. Field of Invention
The present general inventive concept relates to an improved process for producing astaxanthin and astaxanthin-rich algaes and extracts useful as a pharmaceutical, nutraceutical, human or animal food ingredient and for larval fish nutrition.
2. Description of the Related Art
Astaxanthin, a keto-caratonoid, is a phytochemical known as a terpene. Astaxanthin is highly desired as a feed additive in agriculture and aquaculture, as it provides the color and certain antioxidant mechanisms for several fish and animal meats. For example, astaxanthin contributes to the color and antioxidant properties of egg yolks. In nature, animals such as shrimp, krill, zooplankton, and salmon take up and display astaxanthin in their color, and astaxanthin contributes to the antioxidant value of their flesh or biomass. Astaxanthin also provides the red color of various other fish meats, such as trout and several cooked shellfish, such as shrimp, lobster, and the like. Astaxanthin has also become very popular as a pharmaceutical and nutraceutical ingredient.
Astaxanthin occurs naturally, for instance in bacteria, yeasts, and algaes. Haematococcus pluvialis, a fresh water algae, is the largest and most productive known source for producing natural astaxanthin. Astaxanthin concentrations in Haematococcus pluvialis are known to exceed 40,000 parts per million. However, the supply of natural astaxanthin from Haematococcus pluvialis, which consists of only a single stereoisomer, is less than market demand. Astaxanthin is available from several sources and by manufacture of a synthetic production process. However, this results in a mixture of stereoisomers and does not produce the same color in feeds as is desired.
Current production processes for making astaxanthin via controlled growth of algae typically involve setting up a growth phase of algae, typically Haematococcus pluvialis, often in ponds or bioreactors filled with water. Such bioreactors can be indoors using artificial light sources or outdoors using natural sunlight. During this stage of production, typically 8 to 10 days or longer, nutrition is added to the water, such as nitrates, phosphates, sodium and silicates, and the algae is allowed to grow. The grown algae is then subjected to a shock phase in which the algae is subjected to stress, thereby promoting the production of astaxanthin by the algae. Typically, such stress is accomplished by subjecting the algae to nutritional withdrawal in conditions otherwise optimal for photosynthesis, i.e., in the presence of sufficient moisture, warmth, light, and carbon dioxide, and absent competition from other species. For example, in one prior art process, the algae and water is put into a pond with recirculating raceways in an outdoor environment. In these raceways, the gas/water intermix is less than desirable for growth of the algae and turbulence is much less than desirable. Following the shock phase, the algae containing an amount of astaxanthin is harvested. This harvesting process is typically done in three stages. First, the algae and water mixture is centrifuged to remove water. Then, the algae is milled and/or treated with acid to break the algae cells and liberate the astaxanthin. Finally, the broken algae and astaxanthin mixture is spray dried or otherwise prepared for packaging.
The above-described processes for making astaxanthin have several inherent limitations. For example, high losses, cell destruction and death during the growth phase and the stress phase of Haematococcus pluvialis results in low yields of astaxanthin as a percentage of total algal biomass. Whereas astaxanthin should approach or exceed 4% of biomass during the stress phase, it is often much lower due to death and destruction of algae cells. The stress phase, in which the algae cells under stress produce astaxanthin, is understood to be driven by a combination of optimized conditions for photosynthesis and the absence of nutrition. Thus, the stress phase in the above-described process relies on the algae to consume the nutrients in the water to depletion, a long process that leaves many of the cells in a destructive state, resulting in a significant portion of the cells dying. This death and subsequent decay of a portion of the algae cells further results in many contaminants in the algae and water mixture.
Additionally, many of the existing processes for breaking down the cell walls of Haematococcus pluvialis cells are cumbersome and/or destructive. For example, acids are capable of destroying the cell walls of Haematococcus pluvialis cells. However, acids can also degrade the astaxanthin released from the cells. Conventional methods for milling Haematococcus pluvialis cells tend to be imprecise and can result in the introduction of oxidizing sub-processes to the astaxanthin. Too much thermochemical stress through the use of temperature and/or acids can further degrade the astaxanthin through oxidation. For this reason, the current methods of extraction and presentation, storage and processing allow too much degradation of the astaxanthin and do not in the most efficient and effective way prepare it for use.
In light of the above, there is a need in the art for an improved process for producing astaxanthin that includes improved methods and processes for producing astaxanthin-rich algae and improved methods and processes for extracting astaxanthin from the algae. There is need in the art for an improved process that provides a relatively high yield of clean, non-oxidized astaxanthin and that precludes, avoids, or reduces thermochemical stress and contamination of the astaxanthin.